Boston   double action truss rod, 6x9mm bar model, 4mm allen nut, 360mm length, for acoustic guitar

Boston   double action truss rod, 6x9mm bar model, 4mm allen nut, 420mm length, for classic guitar

Boston   double action truss rod, 6x9mm bar model, 4mm allen nut, 460mm length, for electric/acoustic guitar

Boston   double action truss rod, 6x9mm bar model, 4mm allen nut, 590mm length, for bass guitar

Boston   double action truss rod, 6x9mm bar model, 4mm allen nut, 630mm length, for bass guitar